NOTES: Based on data from the Truck Weight Study that are collected by the states for
varying time periods each year and are not adjusted to typify annual averages. Loadings are based on
equivalent single-axle loads (ESALs), a standard unit of pavement damage based on the amount of force
applied to pavement by an 18,000-pound axle, which is roughly equivalent to a standard truck axle.
Raw data are not readily available.

SOURCE: U.S. Department of Transportation, Federal Highway Administration, Highway Statistics
2002 (Washington, DC: 2003), table TC-3, “Percentage Distribution of Traffic Volumes and Loadings
on the Interstate System,” available at http://www.fhwa.dot.gov/policy/ohim/hs02/pdf/tc3.pdf/, as
of February 2004.